Interpretive Summary: Fermentation is being used to produce more and more chemicals, drugs and other products; many of these products have traditionally been made from fossil fuels. A major cost in any fermentation is the cost of the ingredients that are used to feed the microorganisms. So, if fermentation is to be used to produce relatively low value products, low cost feedstocks must be developed. In previous work, we have produced experimental substances that are intended to be lower cost replacements for one component of the feedstock, known as a ‘peptone’. These experimental peptones were derived from rendered protein, that is, materials such as meat and bone meal. Also in previous work, we have shown that some of these experimental peptones serve their purpose by supplying the microorganisms in a fermentation with the nutrients they need to grow well. In the present work, we examined how well the experimental peptones compare to their conventional counterparts in other respects. The tendency of peptones to create undesirable foam in a fermentor, to make the fermentation broth cloudy or highly colored, to make the fermentation broth viscous (thick), and to absorb moisture were all studied. It was found that experimental peptones produced under the right conditions can be equivalent or superior to conventional peptones in any one of these respects. It was not found, however, that any experimental peptone produced to date is equivalent to conventional peptone in all respects simultaneously. The results produced in this study show that low cost feedstocks which perform similarly to their expensive conventional counterparts can be readily produced. The results also provide information vital to the development of low cost feedstocks which will be true equivalents to the conventional products. This success should encourage the further growth of industrial fermentation and the availability of biobased products.

Technical Abstract:
Economic considerations require the use of inexpensive feedstocks for the fermentative production of moderate value products. Our previous work has shown that peptones capable of supporting the growth of various microorganisms can be produced from inexpensive animal proteins, including meat & bone meal, feather meal, and blood meal, through alkaline or enzymatic hydrolysis. In this work, we explore how these experimental peptones compare to commercial peptones in terms of performance characteristics other than chemical make-up; these characteristics can impact fermentation operating cost. It is shown that experimental peptone powders produced through enzymatic hydrolysis are highly hygroscopic and that their physical form is not stable to humid storage conditions; those produced through alkaline hydrolysis and commercial peptones are less hygroscopic. When used in growth medium, all peptones contribute haze to the solution; experiments show that the source of haze is different when using enzyme versus alkali hydrolyzed peptones. Alkali hydrolyzed peptones and all peptones made from blood meal are stronger promoters of media foaming than the commercial peptones; some enzyme hydrolyzed peptones support very little foam formation and are superior to the commercial peptones in this sense. Alkaline hydrolyzed peptones are roughly equivalent to commercial peptones in the coloration they contribute to media, while enzyme hydrolyzed peptones contribute intense coloration to media. No peptone caused a significant change in the viscosity of media. The experimental peptones studied here may be acceptable low cost substitutes for commercial peptones, but none is equivalent to the commercial products in all respects.